***** account being debited without my authorization

Mtn does deserves zero rating. I regret having been a loyal customer for 6 years.Actually l want to stop using their services completely because they are *****sters.l wanted to do an upgrade but because of their incompetence and *****ulent behavior l won't.l called mtn on the 2nd of May to cancel my contract .they suggested an upgrade l agreed but to my surprise they continued debiting same amount as previous contract yet they said they will only debit on new upgrade amount.l called again to cancel and the consultant never did anything. Yesterday l called and the lady who assisted me said she has canceled the contract .l requested for her name and she refused to disclose her name and l was within my rights to know who assisted me.l only discovered today that she did not do anything as well.This is ***** and daylight ******* when they continue to debit my account without my authorization